Physics
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44 Terms
Q: What is a transverse wave?
A: A wave where particles vibrate perpendicular to the direction of travel.
Q: What is a longitudinal wave?
A: A wave where particles vibrate parallel to the direction of travel (compressions + rarefactions).
Q: What is amplitude?
A: Maximum displacement from the rest position.
Q: What is wavelength (λ)?
A: Distance between two identical points on a wave.
Q: What is frequency (f)?
A: Number of waves per second.
Q: How do stationary waves form?
A: Two waves of same frequency travelling opposite directions superpose → nodes + antinodes.
Q: What is a node?
A: A point of no movement.Q: What is an antinode?
Q: What is an antinode?
A: A point of maximum movement.
Q: What are the end conditions of an open pipe?
A: Antinode at both ends.
Q: What are the end conditions of a closed pipe?
A: Node at closed end, antinode at open end.
Q: Why does a closed pipe produce a lower frequency?
A: It supports ¼ wavelengths, giving a longer wavelength, so frequency is lower.
Q: What is an emission spectrum?
A: A set of coloured lines produced when electrons fall to lower energy levels.
Q: Why does each element have a unique emission spectrum?
A: Each element has unique electron energy levels → unique wavelengths = different colours
Q: How do you identify elements in a star?
A: Match the line positions in the star spectrum to known element spectra.
Q: What happens when light enters a denser medium?
A: Slows down and bends towards the normal.
Q: What two conditions are needed for total internal reflection?
A: Light travels from dense → less dense
Angle of incidence > critical angle
Q: Why is cladding used in optical fibres?
A: Reduces energy loss, increases TIR, protects the core.
Q: How do optical fibres transmit images?
A: One bundle sends light in; another returns reflected light; each fibre carries one pixel.
Q: Why might a mobile phone lose signal?
A: Obstacles, interference, absorption, too far from mast.
Q: Why doesn’t Bluetooth interfere with Wi‑Fi?
A: It uses frequency hopping = frequency hopping is when a signal hops rapidly between different radio frequencies,
Q: Why is Bluetooth short‑range?
A: It uses low power, so intensity drops quickly.
Q: What type of waves do mobile phones use?
A: Microwaves.
Q: What is an analogue signal?
A: Smooth, continuous variation.
Q: What is a digital signal?
A: 1s and 0s; discrete levels.
Q: Why is digital better than analogue?
A: Less noise, easier to regenerate, more secure.
Q: What is sampling?
A: Measuring the analogue signal at intervals to convert to digital
Q: Why is high sampling rate important?
A: Produces a more accurate digital copy.
Q: What does a diffraction grating do?
A: Splits light into its component wavelengths by diffraction and interference.
Q: Why do diffraction gratings produce sharp, bright lines?
A: Many slits → more constructive interference → sharper maxima.
Q: What condition produces a bright line?
A: Path difference = nλ (whole number of wavelengths).
Q: Why do different colours appear at different angles?
A: Each wavelength diffracts by a different amount.
Q: How do you identify an element using a diffraction grating?
A: Match the positions of bright lines to known emission spectra.
Q: Why are emission spectra unique?
A: Each element has unique electron energy levels → unique wavelengths.
Q: What happens when light enters a less dense medium?
A: It speeds up and bends away from the normal.
Q: What is refractive index?
A: A measure of how much a material slows down light
Q: What is the critical angle?
A: The angle of incidence where the angle of refraction = 90°.
Q: Why does light refract?
A: Because it changes speed when entering a new medium.
Q: What causes signal loss in fibres?
A: Scattering, absorption, bending of the fibre.
Q: Why are optical fibres good for communication?
A:
Low signal loss
High bandwidth
Immune to electromagnetic interference
Q: Why are microwaves used for satellites?
A: They pass through the atmosphere with little absorption.
Q: Why are uplink and downlink frequencies different?
A: To prevent interference between the two signals.
Q: Why do satellites need to amplify signals?
A: Signals weaken over long distances due to spreading
Q: Why can’t radio waves be used for high‑orbit satellites?
A: They reflect off the ionosphere and don’t reach high altitudes.
Q: Why do low Earth orbit satellites need many satellites?
A: They move quickly → each covers a small area → need a network.